Ink jet recording medium comprising amine-treated silica

ABSTRACT

This invention pertains to an ink jet recording medium comprises a flexible substrate and a coating composition coated on at least one surface of the substrate, wherein the coating composition comprises the product formed from the contact between fumed silica particles and at least one aminoorganosiloxane. The invention also pertains to a method for the preparation of such an ink jet recording medium and to methods for the preparation of a coating composition and a dispersion useful in the preparation of such an ink jet recording medium.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/860,279 filed on May 18, 2001 now U.S. Pat. No. 6,861,115.

FIELD OF THE INVENTION

This invention pertains to an ink jet recording medium comprising aflexible substrate and a coating composition. This invention alsopertains to a method for the preparation of an ink jet recording mediumand to methods for the preparation of a coating composition and adispersion useful in the preparation of an ink jet recording medium.

BACKGROUND OF THE INVENTION

To improve the printing properties of a recording medium, a coatingcomposition is sometimes applied to its surface to form a coatingthereon. For example, a coating can impart a superior feel and aphotograph-like quality to a printed image; a highly absorptive coatingcan reduce the smearing and rub off of an image, and a coating thatimmobilizes (i.e., adsorbs) colorants at the outer surface of thecoating can enhance the waterfastness, sharpness, resolution and colordensity of a printed image.

Coating compositions as described above can be applied to various typesof recording media, including those used in inkjet and laser printingprocesses. In a typical ink jet printing process, a print head scans therecording medium in horizontal strips, using a motor assembly to move itfrom left to right, as another motor assembly rolls the recording mediumvertically through the ink jet printer. As the recording medium is fedvertically through the ink jet printer, ink is emitted from nozzles invertical rows of pixels to eventually form an image. This differs from,for example, a laser printing process where an image is printed (orcopied) onto a recording medium by depositing a uniform electric chargeon a photoconductor drum in the dark; exposing the drum to a pattern oflight, thereby creating a latent image area; developing the pattern byadding toner particles to the latent image area; transferring tonerparticles to the recording medium as it is passed over the drum; fusingthe toner particles to the recording medium by applying heat andpressure thereto; and cleaning the photoconductor drum.

There are several advantages of using an ink jet printing process ascompared to a laser printing (or copying) process. Indeed, ink jetprinting can be done with less expensive hardware and can be used with avariety of different substrates. As a result, the demand for improvedink jet recording media has grown, particularly recording mediaexhibiting the characteristics described above.

It is a challenge, however, to prepare an ink jet recording mediumhaving a coating that is at once glossy, absorptive, and immobilizing.Gloss and colorant immobilization can sometimes be achieved byincorporating different types of polymeric resins into a coatingcomposition. For example, gelatin, polyvinyl pyrrolidone and/orpolyvinyl alcohol can be used to produce glossiness, while a cationicpolymer resin can be used to promote the surface immobilization of ananionic colorant. However, inks applied to polymer-coated ink jetrecording media dry relatively slowly, and often have an undesirabletendency to smear and rub off. While some substances such as certaintreated kaolin clays or treated calcium carbonates can immobilizecolorants, the overall absorptivity and rate of absorption are sometimescompromised with such substances.

Thus, a need remains for an inkjet recording medium having a coatingthat is at once glossy, absorptive, and immobilizing. The presentinvention seeks to provide such a recording medium. These and otheradvantages of the invention will be apparent from the description of theinvention provided herein.

BRIEF SUMMARY OF THE INVENTION

The invention provides an ink jet recording medium comprising a flexiblesubstrate and a coating composition coated on at least one surface ofthe substrate, wherein the coating composition comprises the productformed from the contact between fumed silica particles and at least oneaminoorganosiloxane. The invention also provides a method for thepreparation of an ink jet recording medium.

Furthermore, the invention provides a coating composition for ink jetrecording media, the composition comprising an aqueous vehicle, at leastone binder, and the product formed from the contact between fumed silicaparticles and at least one aminoorganosiloxane. The invention alsoprovides a method for the preparation of a coating composition and amethod for the preparation of a dispersion useful in the preparation ofan ink jet recording medium.

DETAILED DESCRIPTION OF THE INVENTION

This invention pertains to an ink jet recording medium comprising aflexible substrate and a coating composition. The invention alsopertains to a method for the preparation of an ink jet recording mediumand to methods for the preparation of a coating composition and adispersion useful in the preparation of an ink jet recording medium.

The ink jet recording medium comprises a flexible substrate and acoating composition coated on at least one surface of the substrate,wherein the coating composition comprises the product formed from thecontact between fumed silica particles and at least oneaminoorganosiloxane. The ink jet recording medium can be preparedutilizing a method comprising coating at least a portion of the surfaceof a flexible substrate with the product formed from the contact betweenfumed silica particles and at least one aminoorganosiloxane to provide acoated substrate, and drying the coated substrate to produce an ink jetrecording medium.

In addition, the invention provides a coating composition for ink jetrecording media, the composition comprising an aqueous vehicle, at leastone binder, and the product formed from the contact between fumed silicaparticles and at least one aminoorganosiloxane. The coating compositioncan be prepared utilizing a method comprising combining a dispersion of(a) the product formed from the contact between fumed silica particlesand at least one aminoorganosiloxane with (b) at least one binder toproduce the coating composition.

Furthermore, the invention provides a method for the preparation of adispersion useful in preparing an ink jet recording medium, comprising(a) mixing fumed silica particles with an aqueous vehicle under highshear conditions to form a mixture of fumed silica, such that themixture does not coagulate and (b) adding at least oneaminoorganosiloxane to the mixture of (a), so as to form a dispersion ofthe product formed from the contact between the fumed silica particlesand the at least one aminoorganosiloxane.

The fumed silica used in conjunction with the invention enhances theability of the coated flexible substrate to immobilize (i.e., adsorb)and display colorants at the surface of the substrate. The term“colorant” as used herein is meant to encompass both dyes and pigments.In effect, the fumed silica enhances the ability of the coated flexiblesubstrate to immobilize both water-soluble and water insoluble compoundsat the surface of the substrate. The fumed silica comprises fumed silicaparticles that have been contacted with at least oneaminoorganosiloxane. Any suitable aminoorganosiloxane can be used inconjunction with the invention. Suitable aminoorganosiloxanes include,for example, aminoorganosiloxanes of the formula (R¹O)_(n)Si(R²)_(m),wherein R¹ is H, a C₁-C₁₀ alkyl, or a metal ion; R² is an aryl, a C₁-C₁₀alky, or an aralkyl, wherein the aryl, alkyl, and aralkyl aresubstituted with one or more substituents selected from the groupconsisting of amines and quaternary ammonium salts; and n and m are eachintegers equal to or greater than 1, wherein the sum of n and m is 4.Desirably, n is 3 and m is 1, and R² is an alkyl substituted with one ormore substituents selected from the group consisting of amines andquaternary ammonium salts. Therefore, the aminoorganosiloxane used inconjunction with the invention is desirably of the formula (I):

wherein p is an integer from zero to about 100. Preferably, p is aninteger from zero to about 50, and more preferably from zero to about 25(e.g., from zero to about 10, and most preferably either zero or 1). Inaddition to these preferences, it is desirable for R¹ to be H, methyl,or ethyl, and R² to be substituted with a polyamine. A preferredpolyamine is poly(ethyleneimine) or derivatives thereof. In accordancewith these preferences, specific aminoorganosiloxanes that are mostpreferred include 3-aminopropyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,(3-triethoxysilylpropyl)-diethylenetriamine,3-aminopropyltriethoxysilane,N-(2-aminoethyl)-3-aminopropyltriethoxysilane,(3-triethoxysilylpropyl)-diethylenetriamine, and mixtures thereof.

Advantageously, the ink jet recording medium described herein does notrequire the ink jet recording medium to contain thermal imagingchemicals. Typically, recording media utilized in applications such aselectrophotographic imaging, xerographic imaging, and the like require aheat-sensitive fusible layer containing these thermal imaging chemicals,which are mainly composed of a normally electron donating colorless orslightly colored dye precursor and an electron accepting colordeveloper. The dye precursor and the color developer instantaneouslyreact upon application of heat, such as by a thermal head, thermal pen,laser beam, or the like to form an image. For purposes of the invention,it is suitable for the ink jet recording medium of the invention to besubstantially devoid of thermal imaging chemicals. By substantiallydevoid is meant that the ink jet recording medium of the inventioncomprises less than about 0.001 wt. % of thermal imaging chemicals. Itis also suitable for the ink jet recording medium of the invention to becompletely devoid of thermal imaging chemicals. By completely devoid ismeant that the ink jet recording medium contains no thermal imagingchemicals. In certain embodiments, however, such as when an ink jetprinter uses heat and/or pressure to form an image, it is suitable forthe ink jet recording medium to contain thermal imaging chemicals in anamount such that an image can be successful formed on the ink jetrecording medium.

The fumed silica utilized in the invention can be any suitable fumedsilica and typically will be in the form of particles that areaggregates of smaller, primary particles. Although the primary particlesare not porous, the aggregates contain a significant void volume and arecapable of rapidly absorping liquid. These void-containing aggregatesenable a coating of such aggregates to retain a significant capacity forliquid absorption even when the aggregate particles are densely packed,which minimizes the inter-particle void volume of the coating.

The fumed silica particles used in conjunction with the invention can beof any suitable size. Generally, the fumed silica particles have a meandiameter of at least about 100 mn (e.g., particles having a meandiameter of about 100 nm-1 μm, more preferably about 100-500 nm, mostpreferably about 100-400 nm, and especially about 150-250 nm). The fumedsilica can comprise fumed silica particles having any suitable range ofindividual particle diameters, such as a relatively broad range or arelatively narrow range. Preferably, all or substantially all of thefumed silica particles have diameters of at least about 30 nm (e.g., allor substantially all of the particles have diameters of about 30 nm-1μm). The particles also can be monodispersed. By monodispersed is meantthat the individual particles have diameters that are substantiallyidentical. For example, substantially all monodispersed 200 nm particleshave diameters in the range of about 190-210 nm.

It should be noted that the diameter values set forth above for thefumed silica particles refer to the diameters of the aggregates. Withrespect to the primary particles that make up these silica aggregates,it is preferred that the primary particles have a mean diameter of lessthan about 100 nm (e.g., about 1-100 nm). More preferably, the primaryparticles have a mean diameter of less than about 50 nm (e.g., about1-50 nm), even more preferably less than about 30 nm (e.g., about 1-30nm), and most preferably less than about 20 nm (e.g., about 5-15 nm). Inaddition, all or substantially all of the primary particles can havediameters smaller than the mean diameter values set forth above. Inother words, it is preferred that all or substantially all of theprimary particles have diameters of less than about 100 nm (e.g., about1-100 nm), more preferred that all or substantially all of the primaryparticles have diameters of less than about 50 nm (e.g., about 1-50 nm),even more preferred that all or substantially all of the primaryparticles have diameters of less than about 30 nm (e.g., about 1-30 nm),and most preferred that all or substantially all of the primaryparticles have diameters of less than about 20 nm (e.g., about 5-15 nm).

Moreover, the fumed silica can have any suitable surface area. Generallya surface area of about 20-400 m²/g is suitable for the fumed silica.Preferably, the fumed silica has a surface area of about 50-400 m²/g,and, more preferably, the fumed silica has a surface area of about90-330 m²/g, such as about 100-250 m²/g, or even about 150-220 m²/g(e.g., about 180-210 m²/g). The surface area of the fumed silica can bemeasured by any suitable method known in the art. Typically, the surfacearea of the fumed silica is determined by the method of S. Brunauer, P.H. Emmet, and I. Teller, J. Am. Chemical Society, 60, 309 (1938), whichis commonly referred to as the BET method.

The invention involves the use of the product formed from the contactbetween the fumed silica particles and at least one aminoorganosiloxane.The contact between the fumed silica particles and at least oneaminoorganosiloxane can be achieved by any suitable means. For example,an aminoorganosiloxane can be sprayed and optionally heat-treated ontofumed silica particles before being mixed with an aqueous vehicle. It ispreferred, however, that the contact between the fumed silica particlesand at least one aminoorganosiloxane comprises adding at least oneaminoorganosiloxane to the fumed silica particles in a suitable vehicle(e.g., water). The fumed silica particles also can be contacted with atleast one aminoorganosiloxane in a suitable solvent (e.g., water). Forexample, a solution of an aminoorganosiloxane in water can be added toan aqueous mixture of fumed silica particles.

The product formed from the contact between the fumed silica particlesand the at least one aminoorganosiloxane desirably is in the form of adispersion in a suitable vehicle (for example, a liquid carrier such aswater) for subsequent use in preparing the ink jet recording medium. Theproduct particles preferably are stably suspended in the vehicle suchthat the product particles do not settle to the bottom of a container ofthe dispersion for at least about 24 hours when the dispersion isallowed to stand (i.e., without stirring or other agitation) at atemperature of about 25° C. following its preparation.

The dispersion of the product can be prepared by any suitable method.Preferably, the dispersion is prepared by a method comprising (a) mixingfumed silica particles with an aqueous vehicle under high shearconditions to form a mixture of fumed silica, such that the mixture doesnot coagulate, and (b) adding at least one aminoorganosiloxane to themixture of (a), so as to form a dispersion of the product formed fromthe contact between the fumed silica particles and the at least oneaminoorganosiloxane. Mixing under high shear conditions provides an evendistribution of the components of the dispersion, thereby forming asubstantially uniform or homogeneous mixture of the components. Mixingunder high shear conditions also can improve the rheology of thedispersion and can increase the strength and uniformity of any finalarticle prepared from the dispersion. High shear mixers are described inU.S. Pat. Nos. 4,225,247, 4,552,463, 4,889,428, 4,944,595, and5,061,319.

A dispersion of the product formed from the contact between the fumedsilica particles and the at least one aminoorganosiloxane should berelatively stable (i.e., slow to coagulate). The stability of thedispersion can be determined by measuring the viscosity of thedispersion after it is suitably prepared and then allowed to standundisturbed (i.e., without stirring or any other agitation) for acertain length of time. The viscosity can be measured, for example,using a Brookfield LVT viscometer (spindle no. 5, 60 rpm, two minutespin at 25° C.). Alternatively, the viscosity may be measured pursuantto ASTM D 2196 (06.01) entitled “Rheological Properties of Non-NewtonianMaterials by Rotational (Brookfield) Viscometer.” It is preferred thatthe viscosity of the dispersion increases by less than about 50% whenthe dispersion is allowed to stand at a temperature of about 25° C. for60 days, 90 days, 180 days, and/or 270 days immediately following thepreparation thereof.

The aqueous vehicle of the dispersion can be any suitable aqueousvehicle (e.g., carrier). The vehicle of the dispersion preferablycomprises, consists essentially of, or even consists of water, morepreferably deionized water. The vehicle of the dispersion also cancomprise any number of suitable water-miscible liquids, such as one ormore water-miscible alcohols (e.g., methanol, ethanol, etc.) or ketones(e.g., acetone) in addition to water.

The dispersion comprises fumed silica in an amount of about 5-50% byweight (e.g., about 10-30% by weight). For some end uses, the dispersionpreferably has a fumed silica content of at least about 10% by weight(e.g., about 10-50% by weight), more preferably at least about 20% byweight (e.g., about 20%-50% by weight), and most preferably at leastabout 30% by weight (e.g., about 30-50% by weight). For other end uses,such as when a dispersion of maximum stability is desired, thedispersion preferably comprises less than about 35% by weight of fumedsilica (e.g., about 5-35% by weight), more preferably less than about25% by weight (e.g., about 5-25% by weight), and most preferably lessthan about 15% by weight (e.g., about 5-15% by weight).

For many end uses, it is desirable for the dispersion to be of highpurity. Any suitable technique can be employed for that purpose. Onemethod for increasing purity is to pass the dispersion through a filter(e.g., filtering the dispersion) to remove grit and other impuritiesand/or to remove particles above a certain size. For example, thedispersion can be filtered such that particles having a diameter ofabout 1 μm or more are filtered out of the dispersion. In order for adispersion to be filterable, the viscosity of the dispersion must be lowenough such that the dispersion is able to efficiently pass through thedesired filter. The finer the filter (i.e., the smaller the size of thepores of the filter), the lower the viscosity of the dispersion must befor the dispersion to efficiently pass through the filter. As will beappreciated by those of ordinary skill in the art, the dispersion shouldbe passed through as fine a filter as possible to achieve as high adegree of purity as possible but without significantly removing thedesirable fumed silica particles. Thus, it is generally advantageous toproduce a dispersion with a relatively low viscosity, such as describedherein, such that the dispersion can be filtered with a suitably finefilter if desired.

While the inventors do not wish to be bound by any particular theory, itis believed that contacting a fumed silica particle with at least oneaminoorganosiloxane as described herein causes an aminoorganosiloxane tobind to or to otherwise become associated with the surface of the fumedsilica particle, possibly covalently or through an electrostaticinteraction. In other words, the interaction of fumed silica particleswith an aminoorganosiloxane causes the surface of the fumed silicaparticles to become cationically charged. Colorants (i.e., dyes andpigments), such as those used in inkjet inks, often contain ionizablefunctional groups (e.g., SO₃H, COOH, PO₃H₂, etc.), which increase thewater solubility of the dyes or dispersibility of the pigments. Thecolorants become negatively charged when these functional groups ionizein water (e.g., to SO₃ ⁻, COO⁻, PO₃ ²⁻, etc.), and as a resultexperience strong electrostatic attraction to the positive charge of thefumed silica. Therefore, even though the ink can be rapidly absorbedinto the coating via the pores of the fumed silica, the anioniccolorants can be separated from the ink, and immobilized near thecoating surface.

The net charge on the fumed silica particles can be qualitativelydetermined by measuring the zeta potential of the dispersion (e.g.,using a Matec MBS 8000 instrument or a Brookhaven Zeta Plus instrument).The magnitude of the zeta potential is proportional to the magnitude ofthe charge. In addition, negative zeta potential is indicative of a netnegative charge on the fumed silica particles, while a positive zetapotential indicates a net positive charge on the fumed silica particles.The dispersion of the product formed from the contact between the fumedsilica particles and the at least one aminoorganosiloxane, therefore,desirably exhibits a positive zeta potential.

The relative ratio of the total amount of aminoorganosiloxane(s) to thetotal amount of fumed silica must be high enough so that a sufficientamount of the fumed silica particles contact the aminoorganosiloxane(s).Desirably, the fumed silica particles are contacted with at least oneaminoorganosiloxane in an amount of about 0.01-5% by weight of the fumedsilica. It is preferred, however, that the fumed silica particles arecontacted with at least one aminoorganosiloxane in an amount of about0.05-3% by weight, and most preferably in an amount of about 1-3% byweight, of the fumed silica.

Any suitable flexible substrate can be used in conjunction with theinvention. By any suitable flexible substrate is meant that thesubstrate is characterized by properties, which allow it to be usedeffectively in an ink jet printing process. Non-flexible substrates,such as those used in conjunction with a xerographic or laser printingprocesses (e.g., a photoconductor drum), do not exhibit properties whichallow them to be used effectively in an ink jet printing process.Moreover, the flexible substrate can be transparent or opaque and cancomprise any suitable material (such as a polymer). Examples of suchmaterials include, but are not limited to, polyesters (e.g.,poly(ethylene terephthalate)), diacetate resins, triacetate resins,acrylic resins, polycarbonate resins, polyvinyl chloride resins,polyimide resins, cellophane and celluloid, glass sheets, metal sheets,plastic sheets, paper (e.g., cellulose or synthetic paper), photo-basematerial (e.g., paper coated with polyethylene or baryte),pigment-containing opaque films, and foamed films. Preferably, theflexible substrate comprises a polymer film, cellulose paper, or aphoto-base material. When the flexible substrate comprises a polymerfilm, the polymer film is preferably selected from the group consistingof poly(ethylene terephthalate), polyvinyl chloride, or mixturesthereof. When the flexible substrate comprises a paper, the paper ispreferably cellulose paper, and when the flexible substrate comprises aphoto-base material, preferably the photo-base material is coated withat least one coating selected from the group consisting of polyethylene,baryte, and mixtures thereof.

The ink jet recording medium can comprise a flexible substrate havingmore than one layer of coating, which can be the same or different.However, at least one of the coating layers comprises the product formedfrom the contact between fumed silica particles and at least oneaminoorganosiloxane. For example, the ink jet recording medium of theinvention can comprise a flexible substrate coated with one or moreink-receptive layers (e.g., comprising the coating composition describedherein) and/or one or more resinous layers (e.g., a glossy, laminatedsurface layer). Even though the ink jet recording medium of theinvention can comprise such additional layers of coating, it has beenfound that the coating composition of the invention imparts to asubstrate sufficient ink absorption, colorant immobilization, and glosscharacteristics for the vast majority of printing applications.

The ink jet recording medium of the invention can be prepared by coatingat least a portion of the surface of a flexible substrate by anysuitable means with the product formed from the contact between fumedsilica particles and at least one aminoorganosiloxane to provide acoated substrate, and drying the coated substrate by any suitable meansto produce the recording medium. The product formed from the contactbetween fumed silica particles and at least one aminoorganosiloxaneusually will be part of a coating composition.

The coating composition of the invention comprises an aqueous vehicle,at least one binder, and the product formed from the contact betweenfumed silica particles and at least one aminoorganosiloxane. Preferredbinders include, but are not limited to, polyvinyl alcohol, polyvinylacetate, polyvinyl acetal, polyvinyl pyrrolidone, oxidized starch,etherified starch, cellulose derivatives (e.g., carboxymethyl cellulose,hydroxyethyl cellulose, etc.), casein, gelatin, soybean protein,silyl-modified polyvinyl alcohol, conjugated diene copolymer latexes(e.g., maleic anhydride resin, styrene-butadiene copolymer, methylmethacrylate-butadiene copolymers, etc.), acrylic polymer latexes (e.g.,polymers and copolymers of acrylic esters and methacrylic esters,polymers and copolymers of acrylic acid and methacrylic acid, etc.),vinyl polymer latexes (e.g., ethylene-vinyl acetate copolymer),functional group-modified polymer latexes obtained by modifying theaforementioned polymers with monomers containing functional groups(e.g., carboxyl groups), aqueous binders such as thermosetting resins(e.g., melamine resin, urea resin, etc.), synthetic resin binders suchas polymethyl methacrylate, polyurethane resin, polyester resin (e.g.,unsaturated polyester resin), amide resin, vinyl chloride-vinyl acetatecopolymer, polyvinyl butyral, and alkyd resin, with polyvinyl alcoholbeing most preferred. It will be understood that the relative ratio ofthe total amount of organically treated fumed silica to the total amountof binder(s) will depend on the binder used. For example, the optimumratio for polyvinyl alcohol will be different from the optimum ratio forpolyvinyl pyrrolidone.

The coating composition can be prepared by any suitable method.Preferably, the coating composition is prepared by combining adispersion of the product formed from the contact between fumed silicaparticles and at least one aminoorganosiloxane with at least one binderto produce the coating composition. It will be understood that the pH ofthe coating composition can be adjusted at any stage during itspreparation so as to prevent flocculation and/or coagulation of thecoating composition or any component used to produce the coatingcomposition (e.g., a dispersion of fumed silica). For example, the pHcan be adjusted during the preparation of the dispersion before mixingthe dispersion with the at least one binder. It is also suitable for thepH to be adjusted after the dispersion is mixed with the at least onebinder (i.e., after forming the coating composition). In any case, it ispreferred that the pH at any stage during the preparation of the coatingcomposition be about 2-6. In certain embodiments, such as when maximumdispersion stability is desired, it is preferred that the pH at anystage during the preparation of the coating composition be about 3-5,more preferably about 3.5-4.5, such as about 3.5-4. The pH can beadjusted using any suitable method, such as via the addition of an acid(e.g., mineral acid, acidic cation exchange resin, etc.) or a base(e.g., an alkali metal hydroxide, basic anion exchange resin, etc.).

The coating composition can further comprise one or more otheradditives. Suitable additives can include, for example, cationicsurfactants, anionic surfactants (e.g., long-chain alkylbenzenesulfonate salts and long-chain, preferably branched chain,alkylsulfosuccinate esters), nonionic surfactants (e.g., polyalkyleneoxide ethers of long-chain, preferably branched-chain, alkylgroup-containing phenols, polyalkylene oxide ethers of long-chain alkylalcohols, and fluorinated surfactants), hardeners (e.g., active halogencompounds, vinylsulfone compounds, aziridine compounds, epoxy compounds,acryloyl compounds, isocyanate compounds, etc.), pigment dispersants,thickeners, flowability improvers, antifoamers (e.g., octyl alcohol,silicone-based antifoamers, etc.), foam inhibitors, releasing agents,foaming agents, penetrants, coloring dyes, coloring pigments, whiteners(e.g., fluorescent whiteners), preservatives (e.g., p-hydroxybenzoateester compounds, benzisothiazolone compounds, isothiazolone compounds,etc.), antifingal agents, yellowing inhibitors (e.g., sodiumhydroxymethanesulfonate, sodium p-toluenessulfinate, etc.), ultravioletabsorbers (e.g., benzotriazole compounds having a hydroxy-dialkylphenylgroup at the 2-position), antioxidants (e.g., sterically hindered phenolcompounds), antistatic agents, pH regulators (e.g., sodium hydroxide,sodium carbonate, sulfuric acid, hydrochloric acid, phosphoric acid,citric acid, etc.), water-resisting agents, wet strengthening agents,and dry strengthening agents. In addition to these additives, thecoating composition also can comprise a mordant. Suitable mordantsinclude, for example, poly(ethyleneimine), poly(vinylbenzyltrimethylammonium chloride), poly(diallyldimethyl ammonium chloride),and mixtures thereof.

Additional particulates can be added to the coating composition, ifdesired, to further enhance the ability of the ink jet recording mediumto immobilize colorants. Such particulates include, for example, calciumcarbonate, clays, aluminum silicates, urea-formaldehydes, and the like.Other suitable particulates include alumina (e.g., alumina sols,colloidal alumina, cationic aluminum oxide or hydrates thereof,pseudoboehmite, etc.), magnesium silicate, magnesium carbonate, kaolin,talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide,zinc sulfide, zinc carbonate, satin white, diatomaceous earth, calciumsilicate, aluminum hydroxide, lithopone, zeolite, hydrated halloycite,magnesium hydroxide, polyolefins (e.g., polystyrene, polyethylene,polypropylene, etc.), plastics (e.g., acrylic), urea resin, and melamineresin.

The coating composition can be applied to the flexible substrate usingany suitable method or combination of methods to provide the coatedflexible substrate. Suitable methods include, but are not limited to,roll coating, blade coating, air knife coating, rod coating, barcoating, cast coating, gate roll coating, wire bar coating, short-dowelcoating, slide hopper coating, curtain coating, flexographic coating,gravure coating, Komma coating, size press coating in the manner of on-or off-machine, and die coating, with rapid, relatively inexpensivemethods such as rod coating and blade coating being preferred.

After application to the flexible substrate, the coating composition canbe dried using any suitable method or combination of methods to providethe ink jet recording medium. Suitable drying methods include, but arenot limited to, air or convection drying (e.g., linear tunnel drying,arch drying, air-loop drying, sine curve air float drying, etc.),contact or conduction drying, and radiant-energy drying (e.g., infrareddrying and microwave drying).

An image can be recorded on the ink jet recording medium by any suitablemethod. Suitable methods include those known in the art such as drop ondemand methods (e.g., piezo electric or thermal methods) and continuousmethods. Preferably, the method comprises a system whereby ink isreleased from a nozzle and applied to the ink jet recording medium. Theink jet system disclosed in Japanese Patent Document No. 54-59936, inwhich an ink rapidly changes volume due to the action of thermal energyand is ejected from a nozzle by the action of this change of state,effectively can be used in conjunction with the ink jet recording mediumof the invention.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

EXAMPLE 1

This example illustrates the preparation of a dispersion in accordancewith the invention.

A high shear mixer was charged with deionized water (20.2 kg), andhydrochloric acid (36.7 g of 37% concentration). With the mixer running,fumed silica (9.5 kg of 190 m²/g Cab-O-Sil® fumed silica available fromCabot Corporation) was added in sequential amounts and at a constantrate such that the mixture in the aqueous vehicle did not coagulate.After complete addition of the fumed silica, the mixture was furthersubjected to high shear mixing for an additional 75 minutes. Deionizedwater (17.9 kg) was then added to the mixer and mixing continued for anadditional 15 minutes. While the mixer was running,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (54.2 g) was added andsubjected to high shear mixing for 15 minutes so as to produce adispersion of the product formed from the contact between the fumedsilica particles and the amino-organosiloxaneN-(2-aminoethyl)-3-aminopropyltrimethoxysilane. Hydrochloric acid (6.4 gof 37% concentration) was added to the dispersion in order to reduce thepH. The dispersion was subsequently filtered through a nominal 1 μm bagfilter to remove any large particles in the dispersion. The resultingfiltrate had the following properties:

pH 3.7 Solids Content (by weight) 20.0 wt. % Brookfield Viscosoty(spindle 5, 60 rpm) 10 cP Mean Particle Diameter (photon correlationspectroscopy) 124 nm Zeta Potential +26 mV

The dispersion thus prepared has excellent stability for long-term shelflife and storage. The dispersion can be used to form a coatingcomposition, which can be used to produce an ink jet recording mediumthat exhibits good gloss and absorption as well as a superior feel.Moreover, an ink jet recording medium prepared with the coatingcomposition exhibits excellent waterfastness, detailed sharpness, highresolution, and a desirable color density when used in an ink jetprinting process.

EXAMPLE 2

This example illustrates the preparation of an ink jet recording mediumof the invention using a coating composition and methods of theinvention.

A high shear mixer was charged with deionized water (93 kg) andhydrochloric acid (150 g of 37% concentration). With the mixer running,fumed silica (38.9 g of 200 m²/g Cab-O-Sil® fumed silica available fromCabot Corporation) was added in sequential amounts and at a constantrate such that the mixture in the aqueous vehicle did not coagulate.After complete addition of the fumed silica, the mixture of fumed silicain the aqueous vehicle was further subjected to high shear mixing for anadditional hour. Deionized water (57.4 kg) then was added to the mixer,and high shear mixing continued for an additional 10 minutes. While themixer was running, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (221g) was added to the mixer and subjected to high shear mixing for about15 minutes so as to produce a dispersion of the product formed from thecontact between the fumed silica particles and the aminoorganosiloxaneN-(2-aminoethyl)-3-aminopropyltrimethoxysilane. The dispersion wassubsequently filtered through a nominal 1 μm bag filter to remove anylarge particles remaining in the dispersion. The resulting filtrate hadthe following properties:

pH 4.1 Solids Content (by weight) 21 wt. % Brookfield Viscosity (spindle5, 60 rpm) 47 cp Mean Particle Diameter (photon correlationspectroscopy) 139 nm Zeta Potential +36 mV

A 100 g amount of this filtered dispersion was added to a solution ofpolyvinyl alcohol (11.1 g of 30% concentration Airvol 203, Air ProductsInc.) and a 10% solution of a wetting agent (0.8 g Surfactant 10-G, ArchChemicals, Inc.). This mixture was subjected to mixing for approximatelyone minute. The mixture then was placed in a vacuum desiccator atambient temperature (about 20-25° C.) for about one hour to remove anyentrained air bubbles. The resulting coating composition was coated ontotransparent poly(ethylene terephthalate) polymer film using a Number 22Meyer Rod applicator. The resulting coated substrate was dried at 35° C.for about three hours to produce an ink jet recording medium having acoating weight of 10-11 g/m².

The ink jet recording medium produced by the invention exhibited goodgloss and absorption as well as a superior feel. Moreover, the ink jetrecording medium provided printed images with excellent waterfastness,detailed sharpness, high resolution and a desirable color density whenused in an ink jet printing process.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A coating composition for ink jet recording media, the compositioncomprising an aqueous vehicle, at least one binder selected from thegroup consisting of polyvinyl alcohol, polyvinyl acetate, polyvinylacetal, polyvinyl pyrrolidone, oxidized starch, etherified starch,cellulose derivatives, casein, gelatin, soybean protein, silylmodifiedpolyvinyl alcohol, polyvinyl butyral, vinyl chloride-vinyl acetatecopolymer, maleic anhydride resin, melamine resin, and urea resin, andthe product formed from the contact between fumed silica particles andat least one aminoorganosiloxane, wherein the coating composistion has apH of about 2-6.
 2. The coating composition of claim 1, wherein theaminoorganosiloxane is of the formula (R¹O)_(n)Si(R²)_(m), wherein R¹ isH, a C₁-C₁₀ alkyl, or a metal ion; R² is an aryl, a C₁-C₁₀ alkyl, or anaralkyl, wherein the aryl, alkyl, and aralkyl are substituted with oneor more substituents selected form the group consisting of amines andquaternary ammonium salts; and n and m are each integers equal to orgreater than 1, wherein the sum of n and m is
 4. 3. The coatingcomposition of claim 1, wherein the aqueous vehicle is water.
 4. Thecoating composition of claim 1, wherein the at least one binder ispolyvinyl alcohol.
 5. The coating composition of claim 1, wherein thecoating composition further comprises a mordant.
 6. The coatingcomposition of claim 5, wherein the mordant is selected from the groupconsisting of poly(ethyleneimine), poly(vinylbenzyl trimethylammoniumchloride), poly(diallyldimethyl ammonium chloride), or a mixturethereof.
 7. The coating composition of claim 1, wherein the coatingcomposition has a pH of about 3.5-4.5.
 8. The coating composition ofclaim 7, wherein the coating composition has a pH of about 3.5-4.
 9. Thecoating composition of claim 1, wherein the fumed silica particles havea surface area of about 90-330 m²/g.
 10. The coating composition ofclaim 9, wherein the fumed silica particles have a surface area of about150-220 m²/g.
 11. The coating composition of claim 10, wherein the fumedsilica particles have a surface area of about 180-210 m²/g.
 12. A methodof preparing a coating composition for ink jet recording media, themethod comprising combining a dispersion of (a) the product formed fromthe contact between fumed silica particles and at least oneaminoorganosiloxane with (b) at least one binder selected from the groupconsisting of polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal,polyvinyl pyrrolidone, oxidized starch, etherified starch, cellulosederivatives, casein, gelatin, soybean protein, silyl-modified polyvinylalcohol, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer,maleic anhydride resin, melamine resin, and urea resin, to produce thecoating composition, wherein the coating composistion has a pH of about2-6.
 13. The method of claim 12, wherein the aminoorganosiloxane is ofthe formula (R¹O)_(n)Si(R²)_(m), wherein R¹ is H, a C₁-C₁₀ alkyl, or ametal ion; R² is an aryl, an alkyl, or an aralkyl, wherein the aryl,alkyl, and aralkyl are substituted with one or more substituentsselected form the group consisting of amines and quaternary ammoniumsalts; and n and m are each integers equal to or greater than 1, whereinthe sum of n and m is
 4. 14. The method of claim 12, wherein the atleast one binder is polyvinyl alcohol.
 15. The method of claim 12,wherein the method further comprises combining the fumed silicaparticles with at least one mordant.
 16. The method of claim 15, whereinthe at least one mordant is selected from the group consisting ofpoly(ethyleneimine), poly(vinylbenzyl trimethylammonium chloride),poly(diallyldimethyl ammonium chloride), and mixtures thereof.
 17. Themethod of claim 12, wherein the coating composition has a pH of about3.5-4.5.
 18. The method of claim 17, wherein the coating composition hasa pH of about 3.5-4.
 19. The method of claim 12, wherein the fumedsilica particles have a surface area of about 90-330 m²/g.
 20. Themethod of claim 19, wherein the fumed silica particles have a surfacearea of about 150-220 m²/g.
 21. The method of claim 20, wherein thefumed silica particles have a surface area of about 180-210 m²/g.
 22. Amethod of preparing a dispersion useful in preparing an ink jetrecording medium comprising a flexable substrate and a coatingcomposistion coated on at least one surface of the substrate, whereinthe coating composistion comprises the product formed from the contactbetween fumed silica particles and at least one aminooganosiloxane, themethod comprising the steps of (a) mixing fumed silica particles with anaqueous vehicle under high shear conditions to form a mixture of fumedsilica, such that the mixture does not coagulate, and (b) adding atleast one an aminoorganosiloxane to the mixture of (a), so as to form adispersion of the product formed from the contact between the fumedsilica particles and the at least one aminoorganosiloxane, wherein thedispersion has a pH of about 2-6.
 23. The method of claim 22, whereinthe aqueous vehicle is water.
 24. The method of claim 22, wherein theaminoorganosiloxane is of the formula (R¹O)_(n)Si(R²)_(m), wherein R¹ isH, a C₁-C₁₀ alkyl, or a metal ion; R² is an aryl, an alkyl, or anaralkyl, wherein the aryl, alkyl, and aralkyl are substituted with oneor more substituents selected form the group consisting of amines andquaternary ammonium salts; and n and m are each integers equal to orgreater than 1, wherein the sum of n and m is
 4. 25. The method of claim22, wherein the method further comprises, after step (b), (c) filteringthe aqueous dispersion to remove from the dispersion particles having aparticle size of about 1 μm or more.
 26. The method of claim 22, whereinthe dispersion has a pH of about 3.5-4.5.
 27. The method of claim 26,wherein the dispersion has a pH of about 3.5-4.
 28. The method of claim22, wherein the fumed silica particles have a surface area of about90-330 m²/g.
 29. The method of claim 28, wherein the fumed silicaparticles have a surface area of about 150-220 m²/g.
 30. The method ofclaim 29, wherein the fumed silica particles have a surface area ofabout 180-210m²/g.
 31. A coating composistion for ink jet recordingmedia, the composistion comprising an aqueous vehicle, at least onebinder, and the product formed from the contact between fumed silicaparticles and at least aminoorganosiloxane, wherein the coatingcomposistion has a pH of about 2-6 and the fumed silica particles have asurface area of about 150-220 m²/g.
 32. The coating composistion ofclaim 31, wherein the fumed silica particles have a surface area ofabout 180-210 m²/g.
 33. A method of preparing a coating composistion forink jet recording media, the method comprising combining (a) adispersion of the product formed from the contact between fumed silicaparticles and at least one aminoorganosiloxane with (b) at least onebinder to produce the coating composistion, wherein the coatingcomposistion has a pH of about 2-6 and the fumed silica particles have asurface area of about 150-220 m²/g.
 34. The method of 33, wherein thefumed silica particles have a surface area of about 180-210 m²/g.